Transition from Fire-Dependent Open Forests: Alternative Ecosystem States in the Southeastern United States

Brice B Hanberry

doi:10.3390/d13090411

Abstract

Land use and fire exclusion have influenced ecosystems worldwide, resulting in alternative ecosystem states. Here, I provide two examples from the southeastern United States of fire-dependent open pine and pine-oak forest loss and examine dynamics of the replacement forests, given continued long-term declines in foundation longleaf (Pinus palustris) and shortleaf (Pinus echinata) pines and recent increases in commercial loblolly (Pinus taeda) and slash (Pinus elliottii var. elliottii) pines. Shortleaf pine-oak forest historically may have been dominant on about 32 to 38 million ha, a provisional estimate based on historical composition of 75% of all trees, and has decreased to about 2.5 million ha currently; shortleaf pine now is 3% of all trees in the northern province. Longleaf pine forest decreased from about 30 million ha, totaling 75% of all trees, to 1.3 million ha and 3% of all trees in contemporary forests of the southern province. The initial transition from open pine ecosystems to closed forests, primarily comprised of broadleaf species, was countered by conversion to loblolly and slash pine plantations. Loblolly pine now accounts for 37% of all trees. Loss of fire-dependent ecosystems and their foundation tree species affect associated biodiversity, or the species that succeed under fire disturbance.

Highlights

Land use and management practices have changed forest types and characteristics along with ranges and densities of tree species
Old-growth closed forests, old-growth open forests of savannas and woodlands, and old-growth floodplain forests are ecosystems that have been replaced by successional closed forests, plantations, and other land uses such as agriculture
Some tree species are preferred for plantations or landscaping purposes and even have become naturalized in areas outside of historical ranges; for example, conifers have a long history of use for plantings and plantations worldwide [2,3]

Summary

Introduction

Land use and management practices have changed forest types and characteristics along with ranges and densities of tree species. Fire-dependent open forests of savannas and woodlands, and their fire-tolerant tree species component, are historically abundant global ecosystems that have been affected by land use change. I summarized pines are the principal pine species of southeastern mixed forests, due to either current fire-dependent open forests in the southeastern United States and quanti or historical greatest abundances, and all appear to be undergoing continual dynamics in velopments in pine densities and during a 30-year interval, approxi density and potentially in range. Dominant [25] compreh in the southeastern United States, where fires typically occurred every 2 to 15 years at any mented longleaf pine dynamics, but for convenience of comparison, I given place [8,26,27] of Figure 1.

Loss of Fire-Dependent Pine and Pine-Oak Forests and Replacement b

Findings

Implications for Management and Conservation